This invention relates generally to the field of power electronics. More particularly, this invention relates to a technique for utilizing a MOSFET trigger circuit as a silicon-controlled controlled rectifier gate trigger circuit.
High voltage applications of power electronic switches require that many power electronic devices be in series. Each of these devices must have a gate trigger circuit and this circuit must have voltage isolation. This voltage isolation is typically attained by using transformers with isolated windings, which are capable of supplying continuous power to the gate trigger circuit. The power requirements for the gate trigger circuit are based on the power required to fire the silicon-controlled rectifier.
It would be highly desirable to reduce the amount of power that is required in these prior art circuits.
An embodiment of the present invention is a circuit for controlling a silicon-controlled rectifier. The circuit includes a high breakdown voltage metal-oxide semiconductor field-effect transistor (MOSFET) connected to drive the gate of the silicon-controlled rectifier. The high breakdown voltage MOSFET is itself controlled by a gate voltage.
In accordance with the invention, the power requirements for the gate trigger circuit of a series string silicon-controlled rectifier are greatly reduced by using a high breakdown voltage metal-oxide semiconductor field-effect transistor (MOSFET) circuit as a gate triggering circuit for the silicon-controlled rectifier. A limited power source, such as the snubber capacitor voltage that is developed during the OFF-state of the silicon-controlled rectifier can therefore be used to power the gate trigger circuit.